The present invention is concerned with a brake system for use with automotive vehicles, including a vacuum brake force booster operatively located between a brake pedal and a master brake cylinder. The brake force booster comprises at least two working chambers separated from one another by a diaphragm plate, with one of the working chambers being in communication with a vacuum source via a master electro-magnetic valve, and the other working chamber being capable of being vented via a control valve actuable by the brake pedal to generate a brake force in proportion to the brake pedal force.
The inventive brake system includes wheel brake cylinders in communication with the master brake cylinder and sensors associated with the wheels for detecting the rotational behavior of the wheels and determining a locking tendency, the output signals of such sensors being applied to a central electronic controller which, in response to the sensor signals, supplies a switching signal to the master electro-magnetic valve so that the first working chamber is placed in communication with the atmosphere rather than with the vacuum source.
The brake force booster further comprises an auxiliary diaphragm plate fixed to a simulator housing and separating an additional simulator chamber from the booster chamber, the simulator chamber being in permanent communication with the vacuum source and capable of being vented. The brake force booster also includes a piston rod transmitting the brake pedal force which is supported, through a spring, on the simulator housing. The diaphragm plate for generating the brake force is freely displaceable away from the simulator housing.
The present invention further discloses a brake force booster including a front chamber capable of being vented and a rear chamber to which controlled pressure is applied, the chambers being defined by a movable wall and separated from one another by a rolling diaphragm in an air-tight manner, and the rolling diaphragm being in abutment with the side of the wall facing the control pressure chamber.
A brake system and a brake force booster of the above-described type have been taught elsewhere. Venting of the booster chamber has previously been accomplished in a manner such that, through actuation of a control valve by means of a pedal, the communication between a booster chamber and a modulator chamber is initially interrupted and, subsequently, a communication between the booster chamber and the atmosphere is established. Because the control valve is located within a simulator housing, this arrangement requires that a pressure fluid connection be provided between the modulator chamber and corresponding chambers within the control housing. This has been achieved in that the control housing is open towards the front and is sealingly passed through a partition or diaphragm plate between the modulator chamber and the booster chamber.
The above-described design involves a number of disadvantages. For example, two seals are provided for the diaphragm plate, to wit, one for sealing against the housing of the brake force booster and the other for sealing against the simulator housing.
It is, therefore, the object of the present invention to reduce the number of seals required and to thereby attain a system which is less susceptible to said failure.